The present invention refers to a connecting rod-piston mounting arrangement for a reciprocating compressor of the type used in small refrigeration systems, such as refrigerators, freezers, drinking fountains, etc.
The reciprocating compressors known in the art and used in refrigeration systems have a connecting rod, which is mounted, on one side, to an eccentric of a crankshaft journalled to a cylinder block and, on the other side, to a piston reciprocating inside a cylinder, orthogonally in relation to the eccentric axis.
As a function of the small size of the components and the exiguous space provided for mounting the piston-connecting rod-eccentric pin assembly, different constructive alternatives for the connecting rod have arisen, aiming at facilitating the mounting of this assembly to the compressor, such as those alternatives using a two-piece connecting rod, since it is easier to be mounted to the parts defined by the eccentric and the piston.
In these constructions, the parts defined by the connecting rod and the piston are articulated and connected to each other usually by pins, clamps or adhesives.
The known constructions of a two-piece connecting rod have inconveniences, such as: they require a high number of components; they are difficult to assemble; they permit the occurrence of high mass displacement; they generate residues, as in the case of welding or use of adhesive; and they require machining precision, which involves high manufacturing costs. When adhesives are used, there is also the inconvenience of requiring, sometimes, a long drying period. Moreover, the fixation by adhesive compromises the reliability of the product, since the adhesive presents a varying resistance with time, as a function of material aging. In another known constructive solution, the mounting of the connecting rod to the piston occurs by means of a spherical articulation, in which a metallic sphere is affixed, by an adequate process, to one of the ends of the connecting rod. In this construction, the sphere joined to the connecting rod is introduced into a cavity provided inside the piston and mechanically shaped so as to promote a locking of the sphere-connecting rod assembly inside the piston. In some cases, it is also used a fixation means to keep the parts of this assembly together, such as a synthetic resin, which is applied between the sphere and the inner wall of the piston, at the region close to the connecting rod.
This solution has, as disadvantage, the great difficulty in joining the sphere to the end of the connecting rod with quality and in a reliable way, besides causing high localized wear during the operation of the compressor.
Thus, it is an objective of the present invention to provide a connecting rod-piston mounting arrangement for a reciprocating compressor, which allows a simple and fast mounting of the connecting rod-piston assembly, by using components, which do not require high dimensional precision, which do not cause premature wear of the involved parts and which are capable of maintaining the reliability of the product.
A further objective of the present invention is to provide a construction of a connecting rod-piston assembly, in which these parts are kept coupled to each other in a reliable way, without requiring the application of fixation elements therebetween.
These objectives of the invention are attained through a connecting rod-piston mounting arrangement for a reciprocating compressor of small refrigeration systems, in which one of the parts defined by the piston and the end of the connecting rod adjacent the said piston carries a first spherical seat, which is turned to the other part, and a spherical annular seat, which is axially spaced, concentric and turned to the opposite direction in relation to the first spherical seat; the other of said parts incorporating a second spherical seat turned to the first spherical seat and a spherical annular surface seated against the spherical annular seat, the second spherical seat and the spherical annular surface being concentric to the axis of the respective part to which they are incorporated, said first and second spherical seats being seated onto respective opposite spherical surface portions of a ball joint element provided between the piston and the connecting rod, the part incorporating the second spherical seat being radially projected through the spherical annular seat.